Your card isnt running DX10. Vista has to install DX10 and that coveres all others versions. Your card will just run at its hardware limit, DX9.

For all you looking for a great guide, Vista Annoyances Resolved by Koroush Ghazi on Tweakguides has an excellent article your should read even if you don't use vista. http://www.tweakguides.com/VA_1.html
It answeres a lot of questions, especially why you should switch, and explains why to ignore the people saying "VISTA SUCKS" because it really dosen't now. Please read as its very informative.

BTW I'm using Vista x64 and I've been playing the game American McGees ALICE from 2002 and it runs without any patches or tweaking. I love that!

The only issues I have with Vista that don't involve needing a newer PC or hardware are 2-3 things.

1: The User Account Control. People who are comfortable with the PC already will hate this, but for novices this is a great idea. However, it can be turned off.

2: Issues running some games and such. Vista is the most secure version yet, like for example, PC pro's will get this. When I want to end a program, it will ACTUALLY end most of the time, without me having to go to processses and shit to stop it there. Plus it don't blue screen me. The issue though is with some games not running unless you tweak them right.

I also get an error when i quit TF2, but i can still play it, it just says it doesn't react any longer and that windows is going to check for a solution, i always get that when i quit TF2, not while playing or somethhing...

Thanks for all the ideas, I ended up re-installing Steam... twice, so far so good.
Haven't crashed in game just the usual when exiting.

I did run into another little problem, I couldn't access the Steam Community Overlay when I was in the game. I did a little trouble shooting and found that the EVGA Precision On-Screen Display Server was the culprit. If any of you have EVGA cards this is a nice little utility and the OSD allowed me to keep an eye on my core GPU temp while in game. But I'd rather have access to the steam community overlay

Do any of you guys use the console commands to enable multi-threading?
r_threaded_renderables "1" // default 0
mat_queue_mode "2" // default -1